X-ray image sensors using a CCD instead of an X-ray sensitive film are becoming popular as a medical X-ray diagnostic apparatus. In such a radiation imaging system, a radiation detection device having a plurality of pixels acquires two-dimensional image data by radiation as an electrical signal, and this signal is processed by a processor and displayed on a monitor.
As a dental radiation detector used upon insertion into an oral cavity, a radiation detector which is disclosed in JP 10-282243 A has been known. In this radiation detector, an FOP (Fiber Optical Plate) with a scintillator is stuck on the light-receiving surface of a CCD. The radiation detector has a mechanism to convert incident radiation into light by the scintillator, guide the light to the CCD by the FOP, and detect the light.